$ git clone -n https://src.fedoraproject.org/rpms/gnome-font-viewer.git /var/lib/mock/f39-build-1560747-37344/root/chroot_tmpdir/scmroot/gnome-font-viewer
Cloning into '/var/lib/mock/f39-build-1560747-37344/root/chroot_tmpdir/scmroot/gnome-font-viewer'...
$ git fetch origin d93089592c36b7f1adbe2757e2582d8aa2202ae1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-font-viewer
 * [new ref]         d93089592c36b7f1adbe2757e2582d8aa2202ae1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d930895 Update to 45.0